1. Field of the Invention
This invention relates to a motor car traveling control device for controlling the traveling of a motor car on the basis of a tracking type inter-cars distance sensor with a lane change detecting function which measures the distance between a first car on which the sensor is mounted and a second car traveling ahead of it, and detects the lane change of the second car.
2. Description of the Background Art
A sensor for detecting the distance between a first car and a second car ahead of it (hereinafter referred to as "an inter-cars distance sensor", when applicable) has been disclosed, for instance, by Japanese Patent Unexamined Published Application Sho-61-139715. A device for tracking the image of a car ahead has been disclosed, for instance, by Japanese Patent Examined Published Application Sho-60-33352.
FIG. 5 shows the arrangement of the conventional intercars distance sensor. In FIG. 5, reference characters 1R and 1L designate optical systems, namely, lenses; 2R and 2L, twodimensional image sensors; 3, a car ahead the distance from which is to be measured; 6R and 6L, amplifiers; 7R and 7L, analog-to-digital (A/D) converters; 8R and 8L, memories; and 9, an arithmetic processing unit.
The operation of the inter-cars distance sensor will be described. A pair of the image sensors 2R and 2L arranged horizontally or vertically pick up images through the lenses 1R and 1L. The image signals representing the images thus picked up are applied through the amplifiers 6R and 6L to the A/D converters 7R and 7L, respectively, where they are converted into digital data. The digital data are stored in the memories 8R and 8L, respectively.
The arithmetic processing unit 9 makes access to the memories 8R and 8L for image data, to perform arithmetic operations. The arithmetic operations are such that a pair of images are shifted sequentially for correlation. That is, the inter-cars distance can be obtained according to the principle of trigonometrical measurement by using the amount of shift provided when the two images agree best with each other. In the case of FIG. 6, the distance R.sub.0 from a car 3 ahead can be calculated from the following equation: EQU R.sub.0 =L.sub.0 .times.f/C
where L.sub.0 is the base length which is the distance between the optical axes of the two lenses 1R and 1L, f is the focal length of the lenses 1R and 1L, and C is the amount of shift, being equal to the sum of A and B (C=A+B).
With regard to the tracking the object, the device for tracking the image of a car ahead has been disclosed by Japanese Patent Examined Published Application Sho-60-33352. With the device, a window is set in an image displaying screen to track the image of an object to be tracked. With an image signal representing the image in the window as a reference signal, from the image signal obtained upon a slight time has lapse, one which agrees best with the reference is selected, and the deviation thereof is detected, and the direction of the image pickup system is moved so that the object comes into the reference position. The above-described operations are sequentially carried out, so that the image of the object can be tracked in such a manner that it is picked up at the reference position.
On the other hand, Japanese Patent Unexamined Published Application Sho-60-261736 has disclosed a motor car traveling control device as shown in FIG. 7. In FIG. 7, reference numeral 20 designates a microcomputer including a CPU 21, a ROM 22, a RAM 23 and an input/output port 24; 25, a radar unit for transmitting and receiving a radio wave to detect the distance between a car and the one ahead (hereinafter referred to as "an inter-cars distance", when applicable); 26, a vehicle speed sensor; 27, a winker switch; 28, a throttle actuator for actuating a throttle valve; and 29, a transmission actuator for actuating a transmission gear.
The operation of the motor car traveling control device thus organized will be described with reference to FIG. 7. The radar unit 25 is operated to detect the inter-cars distance, while the microcomputer 20 controls the throttle actuator 28 and the transmission actuator 29 so that the inter-cars distance thus detected be a predetermined safe inter-cars distance, thereby to control the vehicle speed detected by the vehicle sensor 26. In addition, the microcomputer 20 receives the output signal of the winker switch 27 to detect the fact that the vehicle is going to change the lane, thereby to set a maximum acceleration.
The conventional devices are designed as described above. Hence, in the case of the device for tracking the image of a car ahead, the image of an object held in the window can be tracked, but it is impossible to measure the distance from the object. In the case of the inter-cars distance sensor, it is impossible for it to track the image of a target. In addition, the inter-cars distance sensor suffers from a difficulty that measurement of the distance from a target is adversely affected by the image signals of objects around the target, so that the distance thus measured includes noticeable error.
In the case of detecting the distance from a target and tracking it, the image of an object moving in space is simply tracked. Hence, when, during measurement of the distance between a first car and a second car ahead of it, the second car ahead changes the traveling lane, the measurement is continued as it is ; however, the fact that the car ahead has changed the traveling lane cannot be detected. Accordingly, if the first car travels at the same speed, then it may collide with another car traveling on the same lane.